Chuck assembly for a rotary power tool

ABSTRACT

A method of operating a power tool chuck assembly includes inserting a tool bit within a central bore of a chuck body, displacing a plurality of jaws with the tool bit from an extended position to a retracted position, displacing the jaws from the retracted position toward the extended position with a spring, rotating a tightening sleeve about a rotational axis in a tightening direction, thereby imparting an axial displacement to the tightening sleeve relative to the chuck body, inwardly displacing a plurality of clamping nuts in a radial direction in response to engagement between a wedge defined on the tightening sleeve and the clamping nuts, causing respective threads on the clamping nuts and the jaws to engage, and applying a clamping force on the tool bit with the jaws in response to continued rotation of the tightening sleeve in the tightening direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/697,948 filed Apr. 28, 2015, which claims priority to U.S.Provisional Patent Application Nos. 61/985,285 and 61/984,994, bothfiled on Apr. 28, 2014, the entire contents of all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to power tools, and more particularly tochuck assemblies for rotary power tools.

BACKGROUND OF THE INVENTION

Power tools having a rotational output (i.e. rotary power tools)typically include chuck assemblies having a plurality of jaws that areadjustable to grip and secure a tool element (e.g., a drill bit).

SUMMARY OF THE INVENTION

The invention provides, in one aspect, a method of operating a chuckassembly for use with a rotary power tool. The method includes insertinga tool bit within a central bore of a chuck body, the bore defining arotational axis, displacing a plurality of jaws with the tool bit froman extended position to a retracted position during insertion of thetool bit within the central bore, displacing the jaws from the retractedposition toward the extended position after insertion of the tool bitwithin the central bore with a spring, rotating a tightening sleeveabout the rotational axis in a tightening direction, thereby impartingan axial displacement to the tightening sleeve relative to the chuckbody, inwardly displacing a plurality of clamping nuts in a radialdirection in response to engagement between a wedge defined on thetightening sleeve and the clamping nuts, causing respective threads onthe clamping nuts and the jaws to engage, and applying a clamping forceon the tool bit with the jaws in response to continued rotation of thetightening sleeve in the tightening direction.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a front end assembly of a power toolincluding a chuck assembly according to an embodiment of the invention.

FIG. 2 is a cross-sectional view of the front end assembly of FIG. 1.

FIG. 3 is an exploded view of the chuck assembly of FIG. 1.

FIG. 4 is a cross-sectional view of a wedge of the chuck assembly ofFIG. 1.

FIG. 5 is a cross-sectional view of the front end assembly of FIG. 1,illustrating a tool bit being inserted within the chuck assembly.

FIG. 6 is a cross-sectional view of the front end assembly of FIG. 1,illustrating the tool bit fully inserted within the chuck assembly.

FIG. 7 is a cross-sectional view of a chuck assembly according toanother embodiment of the invention.

FIG. 8 is a front view of the chuck assembly of FIG. 7.

FIG. 9 is a perspective view of a wedge of the chuck assembly of FIG. 7.

FIG. 10 is a cross-sectional view of the wedge of FIG. 9.

FIG. 11 is another cross-sectional view of the chuck assembly of FIG. 7.

FIG. 12 is another cross-sectional view of the chuck assembly of FIG. 7.

FIG. 13 is a cross-sectional view of a tightening sleeve of the chuckassembly of FIG. 7.

FIG. 14 is a perspective view of a front end assembly of a power toolincluding a chuck assembly according to another embodiment of theinvention.

FIG. 15 is an exploded front view of the chuck assembly of FIG. 14.

FIG. 16 is an exploded rear view of the chuck assembly of FIG. 14.

FIG. 17 is a side view of the chuck assembly of FIG. 14, with portionsremoved, illustrating jaws in a retracted position and, in phantom, anextended position.

FIG. 18 is a cross-sectional view taken along line 18-18 of FIG. 14 withthe chuck assembly in an unlocked configuration and the jaws in theextended position.

FIG. 19 is a cross-sectional view taken along line 19-19 of FIG. 18illustrating clamping nuts in an expanded position disengaged from thejaws.

FIG. 20 is a side view of the chuck assembly of FIG. 14, with portionsremoved, illustrating the chuck assembly in a locked configuration witha tool bit secured between the jaws.

FIG. 21 is a cross-sectional view taken along line 18-18 of FIG. 14 withthe chuck assembly in the locked configuration with a tool bit securedbetween the jaws.

FIG. 22 is a cross-sectional view taken along line 22-22 of FIG. 21 withthe clamping nuts in a contracted position engaging the jaws.

FIG. 23A-23C are enlarged cross-sectional views of the chuck assemblyillustrating a sequence of the chuck assembly being adjusted from theunlocked configuration to the locked configuration.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIG. 1 illustrates a front end assembly 10 for use with a rotary powertool (e.g., a hammer drill, etc., not shown). The front end assembly 10includes a housing 14, a spindle 18 (FIG. 2) supported within thehousing 14 and rotatable about a central axis 22, and a chuck assembly26 for selectively receiving and retaining a tool bit 28 (FIGS. 5 and6). The spindle 18 is coupled to an output 30 of a transmission (notshown), such as a multi-speed, planetary transmission, and receivestorque from an electric motor (not shown) of the rotary power tool. Inthe illustrated embodiment, an adjustable clutch mechanism 34 (FIGS. 1and 2) selectively limits the amount of torque that may be transferredfrom the transmission to the spindle 18.

With reference to FIG. 2, the front end assembly 10 further includes afixed ratchet 38 secured within the housing 14 and a rotatable ratchet42 fixed for co-rotation with the spindle 18 in any of a number ofdifferent ways (e.g., by using an interference fit, welding, etc.). Theratchets 38, 42 are engageable in response to the spindle 18 beingaxially displaced rearward against the biasing force of a spring (notshown) when the rotary power tool is used, for example, in ahammer-drilling operation. Each of the ratchets 38, 42 includes teeth 46that are engageable and slidable relative to each other in response torelative rotation between the ratchets 38, 42. As the teeth 46 on therotatable ratchet 42 slide over the teeth 46 of the fixed ratchet 38,the contour of the teeth 46 impart reciprocation (i.e., “hammering”) tothe spindle 18 to thereby assist the drilling operation. In someembodiments, the spindle 18 may not be reciprocable and the ratchets 38,42 may be omitted. Alternatively, other mechanisms for impartingreciprocation to the spindle 18 may be employed.

A mode selector 50, such as a mode selector ring, may be provided toselectively prevent the ratchets 38, 42 from engaging and impartinghammering action to the spindle 18. The mode selector 50 may alsoselectively enable and disable the clutch mechanism 34. In theillustrated embodiment, the mode selector 50 is rotatable between aplurality of positions corresponding with a driving mode, a drillingmode, and a hammer-drilling mode. In other embodiments, the modeselector 50 may be a lever, button, dial, or any other mechanism.

Referring to FIG. 3, the chuck assembly 26 includes a chuck body 54coupled for co-rotation with the spindle 18, a pusher 58 received withinthe chuck body 54, and a plurality of jaws 62, each having a frontportion or tip 64 and an oblique outer surface 65 extending rearwardfrom the tip 64. In the illustrated embodiment, the chuck assembly 26includes three jaws 62; however, the chuck assembly 26 may include anynumber of jaws 62. The chuck body 54 includes slots 66 in which therespective jaws 62 are received. Each of the slots 66 is oriented at anoblique angle relative to the central axis 22.

Referring to FIG. 2, a shank 70 of the pusher 58 is slidably receivedwithin an axial bore 74 of the spindle 18. Rear portions 78 of therespective jaws 62 are keyed to a front end portion 82 of the pusher 58such that the jaws 62 are coupled for axial movement and co-rotationwith the pusher 58 but are radially movable relative to the pusher 58. Abiasing member or coil spring 86 is disposed between the spindle 18 andthe front end portion 82 of the pusher 58 to bias the pusher 58 (andtherefore the jaws 62) forward, in the direction of arrow A.Accordingly, the spring 86 maintains the jaws 62 in an extendedposition, illustrated in FIG. 2, when there is no tool bit 28 betweenthe jaws 62. In the illustrated embodiment, a rear end of the coilspring 86 is received within an annular recess 90 formed in the spindle18 to stabilize the end of the spring 86.

The chuck assembly 26 further includes a tightening sleeve 94surrounding the chuck body 54 and a wedge 98 disposed between thetightening sleeve 94 and the jaws 62 (FIGS. 2 and 3). The wedge 98 has afrusto-conical interior surface 102 engageable with the outer surfaces65 of the jaws 62 and a frusto-conical exterior surface 106 engageablewith a corresponding frusto-conical interior clamping surface 110 of thetightening sleeve 94. The interior surface 102 of the wedge 98 defines afirst included angle θ1, and the exterior surface 106 of the wedge 98defines a second included angle θ2 that is less than the first angle θ1(FIG. 4). As described in greater detail below, this geometry enablesthe chuck assembly 26 to exert a relatively large clamping force on thetool bit 28 while maintaining a relatively compact size.

The tightening sleeve 94 has internal threads 114 engaged with externalthreads 118 of the chuck body 54 (FIG. 2). Accordingly, rotation of thetightening sleeve 94 relative to the chuck body 54 in a first ortightening direction causes axial displacement of the tightening sleeve94 along the chuck body 54 in the direction of arrow B, thereby applyinga clamping force to the jaws 62 through the wedge 98. Conversely,rotation of the tightening sleeve 94 relative to the chuck body 54 in asecond or loosening direction causes axial displacement of thetightening sleeve 94 along the chuck body 54 in the direction of arrowA. In some embodiments, the threads 114, 118 may have a pitch betweenabout 4 millimeters and about 12 millimeters. In the illustratedembodiment, the threads have a pitch of about 8 millimeters, such that aquarter turn (i.e. a 90 degree rotation) of the tightening sleeve 94relative to the chuck body 54 causes the tightening sleeve 94 totranslate 2 millimeters along the chuck body 54.

With reference to FIGS. 2 and 4, the wedge 98 resolves an axial force,resulting from axial displacement of the sleeve 94, into a normal orclamping force exerted by each of the jaws 62 on the tool bit 28. Ingeneral, the smaller the included angles θ1 and θ2, the greater theclamping force exerted on the tool bit 28. However, the wedge 98 alsogoverns the rate at which the jaws 62 converge on the axis 22 as thejaws 62 and the pusher 58 move from a retracted position toward theextended position illustrated in FIG. 2. A relatively steep angle θ1allows for a shorter, more compact chuck assembly 26. In other words,the greater the first included angle θ1, the less axial distance isrequired for the jaws 62 to fully extend or retract. Therefore, atradeoff exists between the developed clamping force and the length ofthe chuck assembly 26.

In the illustrated embodiment, the first included angle θ1 is about 40degrees, and the second included angle θ2 is about 18 degrees. It hasbeen found through extensive design, calculations, and testing that thisgeometry provides a relatively large clamping force while maintaining acompact length of the chuck assembly 26. In other embodiments, the firstincluded angle θ1 may be between about 30 degrees and about 50 degrees,and the second included angle θ2 may be between about 10 degrees andabout 30 degrees. In yet other embodiments, the second included angle θ2may be between about 2 degrees and about 10 degrees.

In the illustrated embodiment, a retaining ring 122 (e.g., a C-ring) isreceived within a groove 126 formed in the exterior surface 106 of thewedge 98, and the tightening sleeve 94 includes an annular recess 130that surrounds the retaining ring 122 (FIG. 6). As the tightening sleeve94 moves in the direction of arrow A, a rear wall of the recess 130bears against the retaining ring 122. This causes the wedge 98 to movewith the sleeve 94, thereby releasing the clamping force applied to thejaws 62 through the wedge 98.

With reference to FIGS. 5 and 6, to secure a tool bit 28 within thechuck assembly 26, a user pushes the tool bit 28 against the frontportions or tips 64 of the jaws 62, causing the jaws 62 to retract intothe chuck body 54 and compress the spring 86 between the pusher 58 andthe spindle 18 (FIG. 5). The retracting jaws 62 slide along the obliqueslots 66 in the chuck body 54 such that the tips 64 of the jaws 62 moveaway from each other or diverge from the central axis 22. This providesclearance for inserting the tool bit 28 between the jaws 62. Once thereis sufficient clearance between the jaws 62 to accommodate the diameterof the tool bit 28, the tool bit 28 slides into the chuck assembly 26(FIG. 6). Accordingly, tool bits 28 of various sizes may be quicklyinserted into the chuck assembly 26 without requiring any adjustments tothe chuck assembly 26.

Once the tool bit 28 slides into the chuck assembly 26 and between thejaws 62, the spring 86 moves the pusher 58 and the jaws 62 forwardslightly until the exterior surfaces 65 of the jaws 62 contact theinterior surface 102 of the wedge 98, applying a slight clamping forceto the tool bit 28. Next, the user rotates the tightening sleeve 94 inthe tightening direction, causing the tightening sleeve 94 to translatewith respect to the chuck body 54 in the direction of arrow B. Theclamping surface 110 of the tightening sleeve 94 bears against theexterior surface 106 of the wedge 98, causing the wedge 98 to also moveslightly in the direction of arrow B. As the wedge 98 moves in thedirection of arrow B, the interior surface 102 of the wedge 98 bearsagainst the exterior surfaces 65 of the jaws 62 to increase the clampingforce on the tool bit 28. In the illustrated embodiment, the user needonly rotate the tightening sleeve 94 about 90 degrees to securely clampthe tool bit 28.

To release the tool bit 28, the user rotates the tightening sleeve 94 inthe loosening direction, thereby moving the sleeve 94 in the directionof arrow A. As the sleeve 94 moves, a rear wall of the recess 130 bearsagainst the retaining ring 122 on the wedge 98. Accordingly, the wedge98 moves with the tightening sleeve 94 in the direction of arrow A torelease the clamping force exerted on the tool bit 28 through the wedge98 and the jaws 62. The user then grasps the tool bit 28 and withdrawsit from the chuck assembly 26. Once the end of the tool bit 28 clearsthe tips 64 of the jaws 62, the spring 86 moves the pusher 58 and thejaws 62 forward, in the direction of arrow A. The exterior surfaces 65of the jaws 62 bear against the interior surface 102 of the wedge 98,causing the tips 64 of the jaws 62 to converge on the axis 22 until thejaws 62 reach the extended position (FIG. 2).

FIGS. 7-13 illustrate a chuck assembly 226 according to anotherembodiment. This embodiment employs much of the same structure andfeatures as the embodiment of the chuck assembly the chuck assembly 26described above in connection with FIGS. 1-6. Accordingly, the followingdescription focuses primarily upon the structure and features that aredifferent than the embodiment described above in connection with FIGS.1-6. Reference should be made to the description above in connectionwith FIGS. 1-6 for additional information regarding the structure andfeatures, and possible alternatives to the structure and features of thechuck assembly 226 illustrated in FIGS. 7-13 and described below. Inaddition, elements of the chuck assembly 226 that are the same as orsimilar to elements of the chuck assembly 26 described with regard toFIGS. 1-6 are assigned reference numerals based on the referencenumerals for FIGS. 1-6 plus 200.

Referring to FIG. 7, the chuck assembly 226 includes a chuck body 254coupled for co-rotation with a spindle 218 of a rotary power tool. Thechuck assembly 226 further includes a pusher 258 received within thechuck body 254 and a plurality of jaws 262, each having a front portionor tip 264 and an oblique outer surface 265 extending rearward from thetip 264. The respective jaws 262 are received in slots 266 in the chuckbody 254 that are oriented at an oblique angle relative to a centralaxis 222.

The chuck assembly 226 also includes a tightening sleeve 294 surroundingthe chuck body 254 and a wedge 298 disposed between the tighteningsleeve 294 and the jaws 262. In the illustrated embodiment, the wedge298 includes three curved wedge portions 299 interconnected byelastomeric or rubber slugs 301 (FIGS. 8 and 9). The slugs 301 arereceived in grooves 303 located on opposed sides of the respective wedgeportions 299. The slugs 301 may be compressed between adjacent wedgeportions 299 such that the slugs 301 bias the wedge portions 299radially outward and into engagement with the tightening sleeve 294.

Each of the wedge portions 299 includes a track 304 (FIG. 9) having aninterior surface 302 engageable with the outer surface 265 of acorresponding one of the jaws 262 (FIG. 8). Each of the wedge portions299 also includes an exterior surface 306 (FIG. 9) engageable with acorresponding frusto-conical interior clamping surface 310 of thetightening sleeve 294 (FIGS. 7, 11, and 13).

With reference to FIG. 10, the interior surface 302 of each of the wedgeportions 299 defines a first included angle θ1, and the exterior surface306 of each of the wedge portions 299 defines a second included angle θ2that is less than the first included angle θ1. As described in greaterdetail below, this geometry enables the chuck assembly 226 to exert arelatively large clamping force on a tool bit (not shown) whilemaintaining a relatively compact size.

Referring to FIGS. 11-13, the tightening sleeve 294 has internal threads314 engaged with external threads 318 of the chuck body 254 (FIG. 11).The illustrated threads 314, 318 have a trapezoidal or acme profile;however, other thread profiles may be used. Rotation of the tighteningsleeve 294 relative to the chuck body 254 in a first or tighteningdirection causes axial displacement of the tightening sleeve 294 alongthe chuck body 254 in the direction of arrow B, thereby applying aclamping force to the jaws 262 through the wedge portions 299.Conversely, rotation of the tightening sleeve 294 relative to the chuckbody 254 in a second or loosening direction causes axial displacement ofthe tightening sleeve 294 along the chuck body 254 in the direction ofarrow A.

In the illustrated embodiment, the tightening sleeve 294 includes aspiral groove 319 (FIGS. 12 and 13) extending along the root of thetightening sleeve threads 314. A detent 321 located on the chuck body254 is received in the spiral groove 319 to limit rotation of thetightening sleeve 294 relative to the chuck body 254 in the looseningdirection. The detent 321 may be spring biased into engagement with thegroove 319. As the tightening sleeve 294 is rotated, the detent 321slides along the groove 319. When the tightening sleeve 294 isfully-loosened as illustrated in FIG. 12, the detent 321 engages an endof the spiral groove 319 to inhibit further loosening of the tighteningsleeve 294. Accordingly, the tightening sleeve 294 cannot be completelyunthreaded from the chuck body 254.

With reference to FIGS. 7 and 10, the wedge portions 299 resolve anaxial force, resulting from axial displacement of the sleeve 294, into anormal or clamping force exerted by each of the jaws 262 on a tool bit.In general, the smaller the included angles θ1 and θ2, the greater theclamping force exerted on the tool bit. A relatively steep angle θ1,however, allows for a shorter, more compact chuck assembly 226. In otherwords, the greater the first included angle θ1, the less axial distanceis required for the jaws 262 to fully extend or retract. Therefore, atradeoff exists between the developed clamping force and the length ofthe chuck assembly 226.

In the illustrated embodiment, the first included angle θ1 is about 40degrees, and the second included angle θ2 is about 6 degrees. It hasbeen found through extensive design, calculations, and testing that thisgeometry provides a relatively large clamping force while maintaining acompact length of the chuck assembly 226. In other embodiments, thefirst included angle θ1 may be between about 30 degrees and about 50degrees, and the second included angle θ2 may be between about 2 degreesand about 10 degrees.

To apply a clamping force to a tool bit inserted between the jaws 262, auser rotates the tightening sleeve 294 in the tightening direction,causing the tightening sleeve 294 to translate with respect to the chuckbody 254 in the direction of arrow B (FIG. 7). The clamping surface 310of the tightening sleeve 294 bears against the exterior surfaces 306 ofthe wedge portions 299, causing the wedge 298 to also move slightly inthe direction of arrow B. As the wedge 298 moves in the direction ofarrow B, the interior surfaces 302 on the tracks 304 bear against theexterior surfaces 265 of the jaws 262 to increase the clamping force onthe tool bit.

To release the tool bit, the user rotates the tightening sleeve 294 inthe loosening direction, thereby moving the sleeve 294 in the directionof arrow A. As the sleeve 294 moves, a rear wall of a recess 230 in thesleeve 294 bears against a retaining ring 322 circumscribing the wedgeportions 299. Accordingly, the wedge 298 moves with the tighteningsleeve 294 in the direction of arrow A to release the clamping forceexerted on the tool bit through the wedge portions 299 and the jaws 262.The detent 321 prevents the tightening sleeve 294 from being completelyunthreaded from the chuck body 254 (FIG. 12).

FIGS. 14-23 illustrate a chuck assembly 426 according to anotherembodiment. This embodiment employs much of the same structure andfeatures as the embodiment of the chuck assembly 26 and the chuckassembly 226 described above in connection with FIGS. 1-6 and FIG. 7-13,respectively. Accordingly, the following description focuses primarilyupon the structure and features that are different than the embodimentsdescribed above in connection with FIGS. 1-13. Reference should be madeto the description above in connection with FIGS. 1-13 for additionalinformation regarding the structure and features, and possiblealternatives to the structure and features of the chuck assembly 426illustrated in FIGS. 14-23 and described below. In addition, elements ofthe chuck assembly 426 that are the same as or similar to elements ofthe chuck assembly 26 described with regard to FIGS. 1-6 or the chuckassembly 226 described with regard to FIGS. 7-13 are assigned referencenumerals based on the reference numerals for FIGS. 1-6 plus 400.

FIG. 14 illustrates a front end assembly 410 for use with a rotary powertool 412 (e.g., a hammer drill, etc.). The front end assembly 410includes a housing 414, a spindle 418 (FIG. 15) supported within thehousing 414 and rotatable about a central axis 422, and a chuck assembly426 (FIG. 14) for selectively receiving and retaining a tool bit 428.The tool bit 428 is insertable within the chuck assembly 426 along thecentral axis 422 in a rearward direction B and removable from the chuckassembly 426 in a forward direction A. In the illustrated embodiment,the tool bit 428 is a drill bit, but in other embodiments, the tool bit428 may be other types of rotary tool bits (e.g., an impact driver drillor driver bit). The spindle 418 (FIG. 15) is coupled to an output of atransmission (not shown), such as a multi-speed, planetary transmission,and receives torque from an electric motor (not shown) of the rotarypower tool 412. In the illustrated embodiment, an adjustable clutchmechanism 434 (FIG. 14) selectively limits the amount of torque that maybe transferred from the transmission to the spindle 418.

With reference to FIG. 16, the chuck assembly 426 includes a chuck body438 having a threaded portion 440 with which a threaded portion 448 ofthe spindle 418 is engaged. In the illustrated embodiment of the chuckassembly 426, a plug 442 is interference fit to both a central bore 444of the chuck body 438 and an interior portion of the spindle 418,thereby unitizes the spindle 418 to the chuck body 438 for co-rotation.In other words, the interference fit created by the plug 442 preventsthe chuck body 438 from inadvertently unthreading from the spindle 418while the tool 412 is in use. In other embodiments, the plug 442 may bea screw that is threaded into the spindle 418 to fix the chuck body 438and the spindle 418 together. Alternatively, the chuck body 438 and thespindle 418 may be effectively unitized for co-rotation in a differentmanner.

With reference to FIG. 15, the chuck body 438 also includes an annularwall 446 adjacent a shank portion 450, a first outer peripheral portion454 proximate the front end of the chuck body 438, and a second outerperipheral portion 458 between the first outer peripheral portion 454and the annular wall 446. The annular wall 446 includes an annularbearing seat portion 460. The first outer peripheral portion 454includes external threads 456 (FIG. 20), which are discontinuedproximate an interface between the first outer peripheral portion 454and the second outer peripheral portion 458. Stated another way, thesecond outer peripheral portion 458 does not include threads. Withreference to FIGS. 15 and 16, the chuck body 438 also includes aplurality of passageways 462 extending from the central bore 444 andthrough the annular wall 446. In the illustrated embodiment of the chuckassembly 426, the chuck body 438 includes three passageways 462 that areequi-angularly spaced around a periphery of the chuck body 438 (i.e., byabout 120 degrees).

The chuck assembly 426 also includes jaws 466 received through therespective passageways 462. Each of the jaws 466 includes a grippingportion 470 adjacent the front end of the jaw 466, opposed radialgrooves 474 adjacent the rear end of the jaw 466, and threads 476extending between the gripping portion 470 and the grooves 474. Inillustrated embodiment of the chuck assembly 426, the threads 476 oneach of the jaws 466 are configured as double-start buttress threads. Inother words, each tooth of a buttress thread is defined by asubstantially normal (e.g., perpendicular) side 476 a and an obliqueside 476 b (FIG. 23A). For example, the normal side 476 a of each of thethreads is substantially perpendicular to a longitudinal axis 480 of thejaw 466, whereas the oblique side 476 b is oriented at an oblique anglerelative to the longitudinal jaw axis 480. In other embodiments, thethreads 476 may be differently configured as, for example, single-startthreads or triple-start threads. With continued reference to FIG. 23A,the jaws 466 are oriented at an angle θ3 relative to the central axis422, the significance of which is explained in greater detail below.

With reference to FIGS. 15 and 18, the chuck assembly 426 furtherincludes an end cap 478 fixed to the chuck body 438 and the spindle 418for co-rotation therewith. In particular, the end cap 478 is clampedbetween spaced, parallel flanges on the chuck body 438 and the spindle418, respectively. The end cap member 478 includes a surface 482 thatfaces the annular wall 446 of the chuck body 438 (FIG. 18). The chuckassembly 426 also includes a jaw retainer 486 having an annular portion494 slidably received on the shank portion 450 and flanges 498 extendingfrom the annular portion 494. The flanges 498 define a correspondingnumber of slots 502, each of which is sized to slidably receive areduced thickness portion of a jaw 466 defined by between the opposedgrooves 474. Accordingly, the jaws 466 are slidable along the slots 502as the jaw retainer 486 slides along the shank portion 450 of the chuckbody 438. A retaining clip 504 is seated within an annular groove 508(FIG. 18) in the annular portion 494 of the jaw retainer 486, and afirst washer 490 is seated against the retaining clip. A first biasingmember (i.e., coil spring 506) is positioned between the surface 482 ofthe end cap member 478 and the first washer 490 to bias the first washer490, and ultimately the jaw retainer 486, in the forward direction A(FIG. 15).

Alternatively, the first biasing member may be configured as a pluralityof coil springs that are equi-angularly spaced from each other about thecentral axis 422. In further embodiments, the first biasing member maybe configured as a garter spring. In this embodiment, the jaw retainer486 could be omitted (thereby shortening the overall length of the chuckassembly 426), and the garter spring would circumscribe the rear of thejaws 466 to exert a radially inward-directed force on each of the jaws466. Due to the geometry of the passageways 462, a component of theradial force is resolved in the forward direction A, thereby biasing thejaws 466 towards the central axis 422 and the extended position.

With reference to FIGS. 15 and 16, the chuck assembly 426 furtherincludes a plurality of clamping nuts 510 each having interior threads514, an axial keyway 518, and cavities 522. In the illustratedembodiment, three clamping nuts 510 are biased radially outward relativeto the central axis 422 by springs 526. Each spring 526 is seated withina respective cavity 522 of adjacent clamping nuts 510 (FIG. 19). Withreference to FIGS. 15 and 16, the keyways 518 are defined on an exteriorsurface of the respective clamping nuts 510. Similar to the threads 476on each of the jaws 466, the threads 514 on each of the clamping nuts510 are double-start buttress threads. Accordingly, each tooth of thethreads 514 includes a normal side 514 a and an oblique side 514 brelative to the longitudinal axis of the jaw 466. Because the threads514, 476 are also configured as double-start threads, the jaws 466 areaxially displaced a distance of twice the pitch of the threads 476 foreach revolution of the clamping nuts 510. With reference to FIG. 23A,the threads 514 are generally oriented at an angle θ4 relative to thecentral axis 422, whereby the angle θ3 and the angle θ4 aresubstantially equal.

With reference to FIGS. 15 and 16, the chuck assembly 426 also includesa second washer 530 and a thrust bearing 534 in abutting relationshipwith opposite sides of the clamping nuts 510, respectively, with thethrust bearing 534 located between the clamping nuts 510 and the annularwall 446. The thrust bearing 534 is positioned on the annular bearingseat portion 460 and is configured to allow relative rotational movementbetween the clamping nuts 510 and the chuck body 438 while reducingfrictional forces therebetween. The second washer 530 includes acorresponding number of keyways 538 (FIG. 16) that are sized similar toand in alignment with the keyways 518 in the clamping nuts 510.

The chuck assembly 426 also includes a tightening sleeve 542 having keys546 and internal threads 550 (FIG. 15) located on an interior portionthereof. The internal threads 550 are engageable with the externalthreads 456 of the first outer peripheral portion 454. The keys 546 aresized for a snug sliding fit with the keyways 518, 538. In otherembodiments, the keys 546 may include a different geometry toappropriately mate with the keyways 518, 538 in the clamping nuts 510and the washer 530, respectively. With reference to FIG. 18, thetightening sleeve 542 also includes an annular wedge portion 554extending around the entire interior periphery of the tightening sleeve542. The wedge portion 554 defines an oblique angle θ5 relative to thecentral axis 422 (FIG. 23A). In the illustrated embodiment of the chuckassembly 426, the angle θ5 is less than the angles θ3, θ4. Thetightening sleeve 542 also includes axial keyways 558 located on anouter periphery thereof. In the illustrated embodiment, there are threekeyways 558 equi-angularly spaced about the outer periphery of thetightening sleeve 542. Alternatively, the tightening sleeve 542 mayinclude more or fewer than three keyways 558 on its outer periphery. Thechuck assembly 426 also includes a second biasing member (i.e., coilspring 562) seated within a groove 566 proximate a front end of thetightening sleeve 542, and the opposite end of the spring is abuttedwith the second washer 530. The spring 562 is preloaded during all timesof operation of the chuck assembly 426 to bias the second washer 530,the clamping nuts 510, and the thrust bearing 534 in the rearwarddirection B (FIG. 15).

With reference to FIGS. 15 and 16, the chuck assembly 426 furtherincludes an outer sleeve 574, having an insert portion 570 and an outerportion 588, received on the tightening sleeve 542. The insert portion570 is fixed for co-rotation with the outer portion 588 by matingprojections 578 and slots 582 formed in the insert portion 570 and theouter portion 588, respectively. Alternatively, the insert portion 570and the outer portion 588 may be integrally formed as one piece. Theinsert portion 570 includes keys 586 (FIG. 16) equi-angularly spacedabout the central axis 422 and are sized to engage the respectivekeyways 558 in the tightening sleeve 542. The outer portion 588 of theouter sleeve 574 includes a ribbed surface to enhance gripping by theuser. In other embodiments, the outer portion 588 may include a texturedsurface (e.g., a knurled surface) to enhance gripping by the user. Thechuck assembly 426 also includes a front retaining cap 590 interferencefit to the front of the chuck body 438 to thereby clamp the outer sleeve574 between the cap 590 and an annular flange 598 (FIG. 18) on the chuckbody 438 to inhibit movement of the outer sleeve 574 in both the forwarddirection A and the rearward direction B.

In operation, the chuck assembly 426 is adjustable between an unlockedconfiguration (FIGS. 18 and 19), in which a tool bit 428 is insertablebetween the jaws 466, and a locked configuration (FIGS. 20-22), in whichthe tool bit 428 is clamped between the jaws 466. In the unlockedconfiguration of the chuck assembly 426 shown in FIG. 18, the tighteningsleeve 542 is located in a forward position with the internal threads550 of the tightening sleeve 542 engaged with the external threads 456on the first outer peripheral portion 454 of the chuck body 438. Assuch, the wedge portion 554 is disengaged from the clamping nuts 510,providing sufficient radial clearance for the clamping nuts 510 toradially expand within the tightening sleeve 542 under the bias of thesprings 526 (FIG. 19). The amount of radial clearance is sufficient tomaintain the threads 514 of the clamping nuts 510 disengaged from thethreaded portion 476 of the respective jaws 466. In addition, the washer530 and the clamping nuts 510 are biased axially against the thrustbearing 534 by the spring 562 applying (FIG. 18).

With continued reference to FIG. 18, in the unlocked configuration ofthe chuck assembly 426, the jaw retainer 486 and the jaws 466 are biasedin the forward direction A by the spring 506, causing the grippingportions 470 to be in an abutting relationship. Stated another way, inthe unlocked configuration of the chuck assembly 426, the jaws 466default to an extended position.

To insert a tool bit 428 into the chuck assembly 426, a user needs onlyto push the jaws 466 toward a retracted position within the chuck body438 (shown in FIG. 17), against the bias of the spring 506, using theshank of the tool bit 428 itself. As the jaws 466 are retracted withintheir respective apertures 462, the jaw retainer 486 is also slidrearward on the shank portion 450 in unison with the jaws 466. While thejaw retainer 486 is slid rearward, the jaws 466 are slidable radiallyoutward within the slots 502 to create a gap between the grippingportions 470 of the respective jaws 466. This movement of the jaws 466and jaw retainer 486 continues until the gap is sufficiently large toaccept the shank of the tool bit 428, after which time the spring 506rebounds to displace the jaws 466 toward their extended positions tolightly grasp the tool bit 428. As such, the tool bit 428 is initiallyand lightly clamped between the gripping portions 470 of the respectivejaws 466 under the force applied by the spring 506. However, the initialclamping force applied to the tool bit 428 at this time is sufficientlyweak to permit the tool bit 428 to be removed and replaced with adifferent tool bit 428 without requiring the jaws 466 to move to theirretracted position.

In addition, the initial clamping force applied to the tool bit 428 bythe jaws 466 and the spring 506 facilitates self-alignment of tool bitshaving a hexagonal shank between the gripping portions 470.Specifically, when inserting a tool bit having a hexagonal shank intothe chuck assembly 426, an unstable condition naturally results if thegripping portions 470 engage the corners of the hexagonal shank becausethe spring 506 exerts a preload on the jaws 466, a component of which isapplied to the tool bit shank as the initial clamping force describedabove. This instability and application of the initial clamping force onthe tool bit shank causes the hexagonal shank of the tool bit to rotateincrementally until the flats, rather than the corners, of the tool bitshank engage the gripping portions 470.

Once the tool bit 428 is in position and lightly clamped by the jaws 466as described above, the chuck assembly 426 is adjusted to the lockedconfiguration by rotating the outer sleeve 574 in a tightening directionwhich, in turn, also rotates the tightening sleeve 542 in the samedirection. Due to engagement of the threads 550, 456 on the tighteningsleeve 542 and the first outer peripheral portion 454, respectively, thetightening sleeve 542 is also translated in the rearward direction Buntil the threads 550, 456 disengage proximate an interface between thefirst and second outer peripheral portions 454, 458 of the chuck body438. During translation of the tightening sleeve 542 in the rearwarddirection B, the wedge portion 554 engages the clamping nuts 510 toradially contract the clamping nuts 510 within the tightening sleeve 542(against the bias of the springs 526) until the threads 514 of theclamping nuts 510 become engaged with the threads 476 on the jaws 466.

Shortly thereafter, because the external threads 456 are discontinuedproximate the interface between the first and second outer peripheralportions 454, 458 (FIG. 20), further translation of the tighteningsleeve 542 in the rearward direction B is halted even though the outersleeve 574 and the tightening sleeve 542 may continue to be rotated. Inthe illustrated embodiment of the chuck assembly 426, translation of thetightening sleeve 542 in the rearward direction ceases when the wedgeportion 554 has moved past the clamping nuts 510 as shown in FIG. 21,thereby inhibiting further radial contraction of the clamping nuts 510onto the jaws 466. Continued rotation of the outer sleeve 574 and thetightening sleeve 542 in the tightening direction displaces the jaws 466toward their extended positions, increasing the clamping force appliedto the tool bit 428 for securing the tool bit 428 within the chuckassembly 426.

As illustrated in FIG. 23A, while the clamping nuts 510 are beingradially contracted around the jaws 466, the tips of the clamping nutthreads 514 and the tips of the jaw threads 476 could jam and preventthe clamping nuts 510 from properly engaging the jaws 466 whileremaining seated against the thrust bearing 534. However, because thethreads 514 on the clamping nuts 510 and the individual threads in thethreaded portions 476 of the respective jaws 466 are configured asbuttress threads and the angle θ5 defined by the wedge portion 554 isless than the angle θ3 of the jaws, rather than becoming jammed, theclamping nuts 510 may slip in the forward direction A relative to thejaws 466 against the biasing force of the spring 562, opening a gapbetween the clamping nuts 510 and the thrust bearing 534 (FIG. 23B).Thereafter, continued rotation of the outer sleeve 574 and thetightening sleeve 542 in the tightening direction causes the clampingnuts 510 to rotate relative to the jaws 466 and close the gap betweenthe clamping nuts 510 and the thrust bearing 534. Once the gap is closedas shown in FIG. 23C, continued rotation of the outer sleeve 574 and thetightening sleeve 542 in the tightening direction displaces the jaws 466toward their extended positions, increasing the clamping force appliedto the tool bit 428 for securing the tool bit 428 within the chuckassembly 426.

To loosen the jaws 466 and return the chuck assembly 426 to the unlockedconfiguration, the outer sleeve 574 and the tightening sleeve 542 arerotated in an opposite loosening direction, thereby partially retractingthe jaws 466 and relieving the clamping force applied to the tool bit428. As rotation of the outer sleeve 574 and the tightening sleeve 542in the loosening direction continues, the spring 562 urges thetightening sleeve 542 toward the first outer peripheral portion 454 ofthe chuck body 438, causing the threads 550, 456 to re-engage. Asrotation continues, the tightening sleeve 542 is translated in theforward direction A, permitting the clamping nuts 510 to radially expandas the wedge portion 554 moves past the clamping nuts 510 in the forwarddirection A toward the position shown in FIG. 18. Upon the clamping nuts510 reaching the radially expanded position shown in FIGS. 18 and 19,the threads 514, 476 are disengaged, once again permitting the user toreplace the tool bit 428 with a different tool bit 428 in the mannerdescribed above.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A method of operating a chuck assembly for usewith a rotary power tool, the method comprising: inserting a tool bitwithin a central bore of a chuck body, the bore defining a rotationalaxis; displacing a plurality of jaws with the tool bit, from an extendedposition to a retracted position, during insertion of the tool bitwithin the central bore; biasing the jaws, from the retracted positiontoward the extended position, after insertion of the tool bit within thecentral bore with a first spring; rotating a tightening sleeve about therotational axis in a tightening direction, imparting an axialdisplacement to the tightening sleeve relative to the chuck body;inwardly displacing a plurality of clamping nuts in a radial directionin response to engagement between a wedge defined on the tighteningsleeve and the clamping nuts, causing respective threads on the clampingnuts and the jaws to engage; and applying a clamping force on the toolbit with the jaws in response to continued rotation of the tighteningsleeve in the tightening direction.
 2. The method of claim 1, wherein,after engagement of the respective threads on the clamping nuts and thejaws, applying the clamping force on the tool bit by continued rotationof the tightening sleeve in the tightening direction and displacement ofthe jaws toward the extended position.
 3. The method of claim 2, whereinimparting an axial displacement to the tightening sleeve furtherincludes threadably engaging the tightening sleeve with a first outerperipheral portion of the chuck body.
 4. The method of claim 3, furthercomprising moving the tightening sleeve from the first outer peripheralportion to a second outer peripheral portion of the chuck body to stopthe axial displacement of the tightening sleeve.
 5. The method of claim4, wherein moving the tightening sleeve to the second outer peripheralportion prevents overtightening of the clamping nuts on the jaws.
 6. Themethod of claim 4, wherein engaging the tightening sleeve with a firstouter peripheral portion of the chuck body includes engaging externalthreads on the chuck body with internal threads on the tighteningsleeve.
 7. The method of claim 6, wherein moving the tightening sleevefrom the first outer peripheral portion to a second outer peripheralportion of the chuck body includes disengaging the internal threads onthe tightening sleeve from the external threads on the chuck bodyproximate an interface between the first outer peripheral portion andthe second outer peripheral portion of the chuck body.
 8. The method ofclaim 7, wherein moving the tightening sleeve from the second outerperipheral portion to the first outer peripheral portion of the chuckbody includes re-engaging the internal threads on the tightening sleevewith the external threads on the chuck body proximate the interfacebetween the first outer peripheral portion and the second outerperipheral portion of the chuck body.
 9. The method of claim 2, furthercomprising: rotating the tightening sleeve about the rotational axis inan opposite, loosening direction; and releasing the clamping force onthe tool bit.
 10. The method of claim 9, wherein rotating the tighteningsleeve in either the tightening direction or the loosening directionalso rotates the clamping nuts in the tightening direction or theloosening direction, respectively.
 11. The method of claim 9, furthercomprising outwardly displacing the clamping nuts in the radialdirection in response to rotation of the tightening sleeve in theloosening direction, causing the respective threads on the clamping nutsand jaws to disengage.
 12. The method of claim 11, wherein outwardlydisplacing the clamping nuts further includes biasing the clamping nutsin a radial direction with a clamping nut spring positioned betweenadjacent clamping nuts.
 13. The method of claim 1, further comprisingbiasing the clamping nuts in a rearward direction along the rotationalaxis with a second spring.
 14. The method of claim 1, wherein displacingthe jaws from the extended position to the retracted position furtherincludes maintaining a position of the clamping nuts relative to thechuck body during displacement of the jaws from the extended position tothe retracted position.
 15. The method of claim 14, further comprisingcompressing the first spring in response to displacement of the jawsfrom the extended position to the retracted position.
 16. The method ofclaim 1, wherein rotating the tightening sleeve about the rotationalaxis in the tightening direction further includes rotating an outersleeve coupled for co-rotation with the tightening sleeve.
 17. Themethod of claim 16, further comprising translating the tightening sleevealong the rotational axis in response to rotation of the outer sleeveabout the rotational axis.
 18. The method of claim 17, furthercomprising translating the tightening sleeve along the rotational axisrelative to the outer sleeve in response to rotation of the outer sleeveabout the rotational axis.
 19. The method of claim 16, furthercomprising coupling the tightening sleeve for co-rotation with the outersleeve using a key positioned on one of the tightening sleeve or theouter sleeve, and a keyway defined in the other of the tightening sleeveor the outer sleeve.
 20. The method of claim 19, further comprisingsliding the key within the keyway in response to the tightening sleevebeing translated along the rotational axis relative to the outer sleeve,in response to rotation of the outer sleeve about the rotational axis.